{-----------------------------------------------------------------------------
Reactive Banana
------------------------------------------------------------------------------}{-# LANGUAGE Rank2Types, DeriveDataTypeable #-}moduleReactive.Banana.Frameworks(-- * Synopsis-- | Build event networks using existing event-based frameworks and run them.-- * Simple useinterpret,interpretAsHandler,-- * Building event networks with input/output-- $buildNetworkDescription,compile,AddHandler,fromAddHandler,fromChanges,fromPoll,reactimate,initial,changes,liftIO,liftIOLater,-- * Running event networksEventNetwork,actuate,pause,-- * Utilities-- $utilitiesnewAddHandler,newEvent,)whereimportControl.ApplicativeimportControl.Arrow(second)importControl.ConcurrentimportControl.MonadimportControl.Monad.Fix(MonadFix(..))importControl.Monad.IO.Class(MonadIO(..))importControl.Monad.Trans.RWSimportData.Dynamic(Typeable)importData.IORefimportData.List(nub)importData.MonoidimportqualifiedData.HashMap.StrictasMapimportReactive.Banana.Internal.InputOutputimportReactive.Banana.CombinatorsimportqualifiedReactive.Banana.Internal.ASTasASTimportqualifiedReactive.Banana.Internal.PushGraphasImplementationtypeMap=Map.HashMap{-----------------------------------------------------------------------------
AST specific functions
------------------------------------------------------------------------------}inputE::InputChannel[a]->EventtainputE=E.AST.inputE{-----------------------------------------------------------------------------
NetworkDescription, setting up event networks
------------------------------------------------------------------------------}{-$build
After having read all about 'Event's and 'Behavior's,
you want to hook them up to an existing event-based framework,
like @wxHaskell@ or @Gtk2Hs@.
How do you do that?
This "Reactive.Banana.Implementation" module allows you to obtain /input/ events
from external sources
and it allows you perform /output/ in reaction to events.
In constrast, the functions from "Reactive.Banana.Model" allow you
to express the output events in terms of the input events.
This expression is called an /event graph/.
An /event network/ is an event graph together with inputs and outputs.
To build an event network,
describe the inputs, outputs and event graph in the 'NetworkDescription' monad
and use the 'compile' function to obtain an event network from that.
To /activate/ an event network, use the 'actuate' function.
The network will register its input event handlers and start producing output.
A typical setup looks like this:
> main = do
> -- initialize your GUI framework
> window <- newWindow
> ...
>
> -- describe the event network
> let networkDescription :: forall t. NetworkDescription t ()
> networkDescription = do
> -- input: obtain Event from functions that register event handlers
> emouse <- fromAddHandler $ registerMouseEvent window
> ekeyboard <- fromAddHandler $ registerKeyEvent window
> -- input: obtain Behavior from changes
> btext <- fromChanges "" $ registerTextChange editBox
> -- input: obtain Behavior from mutable data by polling
> bdie <- fromPoll $ randomRIO (1,6)
>
> -- express event graph
> let
> behavior1 = accumB ...
> ...
> event15 = union event13 event14
>
> -- output: animate some event occurences
> reactimate $ fmap print event15
> reactimate $ fmap drawCircle eventCircle
>
> -- compile network description into a network
> network <- compile networkDescription
> -- register handlers and start producing outputs
> actuate network
In short, you use 'fromAddHandler' to obtain /input/ events.
The library uses this to register event handlers
with your event-based framework.
To animate /output/ events, use the 'reactimate' function.
-}typeAddHandler'=AddHandlerInputValuetypePreparationst=([Eventt(IO())]-- reactimate outputs,[AddHandler']-- fromAddHandler events ,[IOInputValue]-- fromPoll events,[IO()]-- liftIOLater)-- | Monad for describing event networks.-- -- The 'NetworkDescription' monad is an instance of 'MonadIO',-- so 'IO' is allowed inside.-- -- Note: The phantom type @t@ prevents you from smuggling-- values of types 'Event' or 'Behavior'-- outside the 'NetworkDescription' monad.newtypeNetworkDescriptionta=Prepare{unPrepare::RWST()(Preparationst)()IOa}instanceMonad(NetworkDescriptiont)wherereturn=Prepare.returnm>>=k=Prepare$unPreparem>>=unPrepare.kinstanceMonadIO(NetworkDescriptiont)whereliftIO=Prepare.liftIOinstanceFunctor(NetworkDescriptiont)wherefmapf=Prepare.fmapf.unPrepareinstanceApplicative(NetworkDescriptiont)wherepure=Prepare.puref<*>a=Prepare$unPreparef<*>unPrepareainstanceMonadFix(NetworkDescriptiont)wheremfixf=Prepare$mfix(unPrepare.f){- | Output.
Execute the 'IO' action whenever the event occurs.
Note: If two events occur very close to each other,
there is no guarantee that the @reactimate@s for one
event will have finished before the ones for the next event start executing.
This does /not/ affect the values of events and behaviors,
it only means that the @reactimate@ for different events may interleave.
Fortuantely, this is a very rare occurrence, and only happens if
* you call an event handler from inside 'reactimate',
* or you use concurrency.
In these cases, the @reactimate@s follow the control flow
of your event-based framework.
-}reactimate::Eventt(IO())->NetworkDescriptiont()reactimatee=Prepare$tell([e],[],[],[])-- | A value of type @AddHandler a@ is just a facility for registering-- callback functions, also known as event handlers.-- -- The type is a bit mysterious, it works like this:-- -- > do unregisterMyHandler <- addHandler myHandler---- The argument is an event handler that will be registered.-- The return value is an action that unregisters this very event handler again.typeAddHandlera=(a->IO())->IO(IO())-- | Input,-- obtain an 'Event' from an 'AddHandler'.---- When the event network is actuated,-- this will register a callback function such that-- an event will occur whenever the callback function is called.fromAddHandler::AddHandlera->NetworkDescriptiont(Eventta)fromAddHandleraddHandler=Prepare$doi<-liftIO$newInputChannelletaddHandler'k=addHandler$k.toValuei.(\x->[x])tell([],[addHandler'],[],[])return$inputEi-- | Input,-- obtain a 'Behavior' by frequently polling mutable data, like the current time.---- The resulting 'Behavior' will be updated on whenever the event-- network processes an input event.---- This function is occasionally useful, but-- the recommended way to obtain 'Behaviors' is by using 'fromChanges'.-- -- Ideally, the argument IO action just polls a mutable variable,-- it should not perform expensive computations.-- Neither should its side effects affect the event network significantly.fromPoll::IOa->NetworkDescriptiont(Behaviorta)fromPollpoll=Prepare$doi<-liftIO$newInputChannelletpoll'=toValuei.(:[])<$>polltell([],[],[poll'],[])initial<-liftIO$pollreturn$stepperinitial(inputEi)-- | Input,-- obtain a 'Behavior' from an 'AddHandler' that notifies changes.-- -- This is essentially just an application of the 'stepper' combinator.fromChanges::a->AddHandlera->NetworkDescriptiont(Behaviorta)fromChangesinitialchanges=stepperinitial<$>fromAddHandlerchanges-- | Output,-- observe when a 'Behavior' changes.-- -- Strictly speaking, a 'Behavior' denotes a value that varies *continuously* in time,-- so there is no well-defined event which indicates when the behavior changes.-- -- Still, for reasons of efficiency, the library provides a way to observe-- changes when the behavior is a step function, for instance as -- created by 'stepper'. There are no formal guarantees,-- but the idea is that---- > changes (stepper x e) = return (calm e)changes::Behaviorta->NetworkDescriptiont(Eventta)changes~(B(AST.Pair_(AST.Stepperxe)))=return$E$fmap(:[])e-- | Output,-- observe the initial value contained in a 'Behavior'.---- Similar to 'updates', this function is not well-defined,-- but exists for reasons of efficiency.initial::Behaviorta->NetworkDescriptiontainitial~(B(AST.Pair_(AST.Stepperxe)))=returnx-- | Lift an 'IO' action into the 'NetworkDescription' monad,-- but defer its execution until compilation time.-- This can be useful for recursive definitions using 'MonadFix'.liftIOLater::IO()->NetworkDescriptiont()liftIOLaterm=Prepare$tell([],[],[],[m])-- | Compile a 'NetworkDescription' into an 'EventNetwork'-- that you can 'actuate', 'pause' and so on.compile::(forallt.NetworkDescriptiont())->IOEventNetworkcompile(Preparem)=do-- execute the NetworkDescription monad(_,_,(outputs,inputs,polls,liftIOs))<-runRWSTm()()sequence_liftIOslet-- union of all reactimatesEgraph=foldrunionneveroutputsautomaton<-Implementation.compileToAutomatongraph-- allocate new variable for the automatonrautomaton<-newEmptyMVarputMVarrautomatonautomatonlet-- run the graph on a single input valuerun::InputValue->IO()runinput=do-- takeMVar makes sure that event graph updates are sequential.automaton<-takeMVarrautomaton-- poll mutable datapollValues<-sequencepolls-- percolate inputs through event graph(reactimates,automaton')<-runStepautomaton$input:pollValuesputMVarrautomatonautomaton'-- Run corresponding IO actions afterwards.-- Under certain circumstances, they can *interleave*.casereactimatesofJustactions->sequence_actionsNothing->return()-- register event handlersregister::IO(IO())register=fmapsequence_.sequence.map($run)$inputsmakeEventNetworkregister{-----------------------------------------------------------------------------
Running event networks
------------------------------------------------------------------------------}-- | Data type that represents a compiled event network.-- It may be paused or already running.dataEventNetwork=EventNetwork{-- | Actuate an event network.-- The inputs will register their event handlers, so that-- the networks starts to produce outputs in response to input events.actuate::IO(),-- | Pause an event network.-- Immediately stop producing output and-- unregister all event handlers for inputs.-- Hence, the network stops responding to input events,-- but it's state will be preserved.---- You can resume the network with 'actuate'.---- Note: You can stop a network even while it is processing events,-- i.e. you can use 'pause' as an argument to 'reactimate'.-- The network will /not/ stop immediately though, only after-- the current event has been processed completely.pause::IO()}deriving(Typeable)-- Make an event network from a function that registers all event handlersmakeEventNetwork::IO(IO())->IOEventNetworkmakeEventNetworkregister=doletnop=return()unregister<-newIORefnopletactuate=register>>=writeIORefunregisterpause=readIORefunregister>>=id>>writeIORefunregisternopreturn$EventNetworkactuatepause{-----------------------------------------------------------------------------
Simple use
------------------------------------------------------------------------------}-- | Simple way to run an event graph. Very useful for testing.-- Uses the efficient push-driven implementation.interpret::(forallt.Eventta->Eventtb)->[a]->IO[[b]]interpretfxs=dooutput<-newIORef[](addHandler,runHandlers)<-newAddHandlernetwork<-compile$doe<-fromAddHandleraddHandlerreactimate$fmap(\b->modifyIORefoutput(++[b]))(fe)actuatenetworkbs<-forMxs$\x->dorunHandlersxbs<-readIORefoutputwriteIORefoutput[]returnbsreturnbs-- | Simple way to write a single event handler with functional reactive programming.interpretAsHandler::(forallt.Eventta->Eventtb)->AddHandlera->AddHandlerbinterpretAsHandlerfaddHandlerA=\handlerB->donetwork<-compile$doe<-fromAddHandleraddHandlerAreactimate$handlerB<$>feactuatenetworkreturn(pausenetwork){-----------------------------------------------------------------------------
Utilities
------------------------------------------------------------------------------}{-$utilities
This section collects a few convenience functions
for unusual use cases. For instance:
* The event-based framework you want to hook into is poorly designed
* You have to write your own event loop and roll a little event framework
-}-- | Build a facility to register and unregister event handlers.newAddHandler::IO(AddHandlera,a->IO())newAddHandler=dohandlers<-newIORefMap.emptyletaddHandlerk=dokey<-newUniquemodifyIORefhandlers$Map.insertkeykreturn$modifyIORefhandlers$Map.deletekeyrunHandlersx=mapM_($x).mapsnd.Map.toList=<<readIORefhandlersreturn(addHandler,runHandlers)-- | Build an 'Event' together with an 'IO' action that can -- fire occurrences of this event. Variant of 'newAddHandler'.-- -- This function is mainly useful for passing callback functions-- inside a 'reactimate'.newEvent::NetworkDescriptiont(Eventta,a->IO())newEvent=do(addHandler,fire)<-liftIO$newAddHandlere<-fromAddHandleraddHandlerreturn(e,fire)